Gigantic OTN
by Ren the Banana
Summary: "If you lie about it, I'll shoot you with a 40-caliber pistol." Those were the words of Rin Kagamine's twin brother, Len, after he had given his sister all he had. Rin has decided she truly loves Len and they were made for each other, but does Len really love Rin for who she is? (Continuation of my previous fanfic, Plus Boy. Original song by Giga-P and Reol.)
1. Prologue

_"_ _Ahh…please…be gentle with me…"_

 _"_ _Are you sure about this?"_

 _"_ _Y-yes. I'm sure…but what if Mom and Dad find out?"_

 _"_ _They won't. They're out on a date at a restaurant."_

 _"_ _Okay then…you can start…"_

He started to slide inside her and began to thrust. Her moans echoed through out the room.

The boy put a finger to his girlfriend's lips. "If Mom and Dad come in without us knowing, we're dead." She nodded quickly. After all, he was her younger twin brother. And she was only 14.

"Aahh…it hurts…"

The girl screamed in pain, her fingernails scratching her brother's back. He winced. This was so much like her. Although her face, he thought, was really cute at the moment. She was squinting, blinking back tears. Concerned, he stopped for a moment. He smirked. "What's wrong?" he asked sarcastically. "Am I going too hard on you?"

His twin took a deep breath. "N-no, I'll be fine…" Her brother had started to feel a little sympathy for her. This was her first time, as was his. He sighed. "Alright, what about you go on top of me, then move?" he said, running a hand through his hair. She smiled. "Alright, I guess…" was her reply.

She toyed around with his dick for a moment. "I made a mistake to call it tiny a few months ago when I had never actually seen it…" she said, amazed. He grinned. "Yeah, you did." he responded. She shot him a glare. He cringed. This was his sister, after all.

When she had all of him inside her, she winced once again. It still hurt, but she was confident, as this was her big moment to prove herself to him. She started to move. Her younger twin moaned. "A-ahh…I…It's already…" he screamed, feeling his sister's warmth. She blushed. He was already almost at it?

 _"_ _I…I'M SO HAPPY YOU'RE DOING THIS WITH ME…SIS!"_

 _"_ _A…AH, ME TOO?!"_

 _"_ _I'M GOING TO…"_

 _"_ _AAAAYAAAAGGGHHHHH!"_

His fluids shot out as his sister pulled him out of her. She smiled. Even though he was already her boyfriend and was turning fifteen this year, he was still the same childish twin brother she was with all her life.

"Um," she said, smiling. She blushed. "I…I love you…so much…" The words came out of her mouth. He grinned and sat down in front of her.  
"Yeah? Well…I also needed to ask you something…" he replied, trailing kisses down her neck, then receiving a slap in reward. She looked at him. He smirked. "Sis…"

"What do you think of my O.T.N?" he asked. His sister turned red. How was she supposed to respond to that?! She took a look at it and covered her face in embarrassment. He patted her head. She was so cute…

She tucked a lock of hair under her ear and thought about it for a while. "Um, well…" she began, trying not to nosebleed, "It…It's big…I guess?"

He lied down on the bed, followed by the girl flopping down beside him. He put a hand on her face. "Is that all?" he asked, attempting to seduce her, although his older twin knew him too well. She had no words. There was silence.

"Well, I have news for you…" he continued, licking his lips. She backed away a little, receiving a hug in response.

 ** _"_** ** _If you lie about how gigantic it is, I'll shoot you with a 40-caliber pistol."_**


	2. Chapter 1 - The Pervert

_"_ _Hmm…Rin-chan…you smell so good…"_

Rin Kagamine lay in her bed, still asleep. She woke up to the feeling of someone touching her breast. She sat up quickly, and realised it was just her twin brother, Len. He was half asleep, groping her.

It then hit her. Why was he in her bed?!

She slapped him "I'm awake now, you doofus!" she yelled, annoyed. Len grinned and hugged her. "Good morning, Rin! I…um, just thought you looked really cute…" he said, trying to hide the fact he had just sneaked into her room to possibly rape her. Rin rolled her eyes. He was always like this. "Um, then why are you in my room?!" she said, ready to slap Len once again. Her brother blushed and tried to grin happily, while she smirked. One day she was going to get a steamroller and make him flat as a pancake, she vowed.

She then looked down. There was a bulge in his "area". Rin cringed. "Len," she said, trying not to lose her cool, "Your banana is showing…" He turned red and put his hands over his crotch. "U-um, well, let's get ready for school…" he stammered, heading for the bathroom. Rin laughed. "Yes, let's. I don't want to be late for the first day of the school year because my brother was busy being a pervert and had boner problems." she said, getting out of bed. It was the first day of 9th Grade, and she had wanted to make a good impression.

Rin smiled to herself and thought for a while. Len…he was cute, but a massive pervert. She had remembered once at school he had flipped her skirt while she was talking to her friends. He had a lot of explaining to do afterwards.

She bit her lip in annoyance. And he was still talking to her about how her panties had oranges all over them. Stupid.

He had promised to her he'd try to get married with her, although she assured him that wasn't possible, as they were siblings related by blood. Rin felt the same, somehow, but it would just make things harder, her parents didn't even know they were dating each other, and that they were already a couple. If they had married, they would have probably kicked them out of the house.

Rin sighed and started to fix her hair. Once Len had already finished, he decided to wait for her, as always.

When the siblings arrived at school, a girl immediately rushed to hug Len. It was Miku, one of the twins' friends.

Miku grinned from ear to ear. "Len! I'm so glad you're back~" she said happily. She looked over to Rin and squeezed her cheeks. "Rin-chan! Ah…has your hair gotten longer?" she asked curiously. Rin rolled her eyes. "Miku, it's only been a few weeks. The school holidays aren't that long…" she said.

"Ah, if it isn't Rin-chan and Len-kun."

A tall, slender girl walked over to them, her long pink hair trailing behind her. "Luka-chan!" Rin exclaimed, rushing over to her friend. The two talked for a while, then Luka smiled warmly at Len. "Len, it's so good to see you again!" she said. Len grinned. Luka had been one of his past crushes, before he fell in love with Rin.

When they got home, Rin had noticed something. Len had been quiet recently. Still perverted, but quiet. This wasn't like him. Instead of hanging out with her, he had stayed in his room and wouldn't come out.

Rin had started to think. Was there something wrong? Or was he doing "it" again? She blushed and tried not to think about it, then decided she would take the risk and listen.

She leaned against the door and pressed her ear, but then the door had creaked wide open, making Rin fall to the ground. Len had been careless enough to not close the door properly. There was Len, who had immediately realized Rin was there. He was in bed…in his boxers.

Rin turned red as a strawberry and was about to get out as fast as she could. "ABORT, ABORT, ABORTTT!" she wanted to scream.

"Rin…?" the blonde asked, wondering why his sister was lying on the ground in front of the door. Rin got up and tried not to focus on his lower area. Len stood up and walked over to her. "U-um, I can explain!" Rin stammered, trying to get the words out. "I…I was concerned, okay?! Y-you were in your room for a really long time…without me…" Her head hung down in shame as she realised she had only wanted to listen in to what he was doing, she was as bad as him.

Len hugged his sister. "Rin…I'm fine, okay? I just wanted to have some free time to myself. I'm sorry…" he said, kissing her forehead. Rin blushed, then realised she could feel his lump on her knee. She squinted and tried not to think about it.

He immediately realised what she was looking at and a smile flickered across his face. "Rin…is something wrong?" he asked, smirking. She shook her head rapidly. "N-no…" she said, turning red. She squeaked out when she felt Len squeeze her right breast. Her twin grinned. "They haven't grown much, but small is cute, too." he said. His tongue quickly brushed the nape of her neck, causing her to slip out a tiny moan. "N-not now, Len…" Rin said, although a part of her was enjoying it. He took her hand and they both stood up. He led her to his bed, and she sat on it. Rin looked at Len with a worried expression. "Len…what if…what if Mom and Dad find out? They'd kill us…" she said in a shaky voice. Len stood up to lock the door and looked back to his sister. "They won't," he said in a quiet voice, "they're at a restaurant at the moment. Although just to keep things safe, I'm locking the door."

Rin nodded sheepishly as her brother walked back to the bed and sat beside her. "Should we begin now?" he asked, a smirk on his face. Rin smiled and nodded. This was her big chance. Her chance to prove to Len how much she loved him.

Len put his hand on her head and smiled, with tears in his eyes. "Rin…" he said, overwhelmed, "You have no idea how happy this makes me…" He laid her on the bed and kissed her. Rin moaned. Their tongues danced around, making Rin shake. She clutched the bedsheets and felt herself getting wet already. How was it already like this? They were just ordinary siblings…then fell in love with each other, started dating, and now they were doing it…and they were only fourteen going on fifteen.

Rin put her hand on her panties. They were already soaking wet…just from Len's kiss. Her twin looked at where she was touching and ended the kiss, smiling. "Touching yourself already? Rin…I never knew how horny you were…" he said, tracing his finger on her panties. Rin winced.

 _This…was only the beginning._

 ** _~Afterword~_**

 ** _Yay, first chapter done! Ahh, Len, you pervert! (swoon~) Ahahaha, this was quite fun to write about. Our Len-kun from Plus Boy has become a...very seductive boy. (but perverted)_**

 ** _I will see you people later! Byeeee~_**


End file.
